1. Field of the Invention
The present invention relates to a novel catalyst for producing an aromatic vinyl compound polymer and a process for producing an aromatic vinyl compound polymer by using the same. More particularly, it pertains to a novel catalyst which comprises a trivalent titanium compound and is capable of efficiently producing a polymer or a copolymer of an aromatic vinyl compound having a high degree of syndiotactic configuration in its aromatic vinyl chain of the polymer or copolymer (hereinafter sometimes referred to generically as "(co)polymer") and a process for producing a polymer or a copolymer of an aromatic vinyl compound by the use of said catalyst.
2. Description of the Related Arts
Heretofore, styrenic polymers produced by the radical polymerization method or the like have an atactic configuration in stereostructure and are molded to various shapes by various molding methods such as injection molding, extrusion molding, blow molding, vacuum molding and cast molding, and they have been widely used as domestic electrical appliances, office machines, household goods, packaging containers, toys, furnitures, synthetic papers, sheets, films and other industrial materials.
However, such styrenic polymers having atactic configuration have disadvantage that it is inferior in heat resistance and chemical resistance.
The group to which the present inventor belongs has previously succeeded in developing styrenic polymers having a high degree of syndiotacticity (see Japanese Patent Application Laid-Open Nos. 187708/1987, 179906/1988, 241009/1988, 249504/1992 etc.).
Since the styrene polymers having a syndiotactic configuration have melting points which are different from those of the conventional atactic polystyrenes, and are higher than those of the isotactic polystyrenes known so far, they are expected to be used as heat-resistant resins in various field.
However, in order to obtain a high performance catalyst capable of efficiently producing a styrenic polymer having a syndiotactic configuration, it has heretofore been necessary to prepare the catalyst by the use of a tetravalent titanium complex, thus complicating the preparation procedures including synthesis and purification and generally lowering the synthetic efficiency. On the other hand, the use of a catalyst prepared by using a trivalent titanium compound results in a decrease in the catalytic activity and in the formation of a styrenic polymer having a low degree of syndiotacticity and/or mixture of a styrenic polymer having a syndiotactic configuration and a styrenic polymer having an atactic configuration (refer to Japanese Patent Application Laid-Open No. 120706/1988). In general, the use of a tetravalent titanium complex brings about lowering of the melting point of the resultant polymer, that is, the loss of the characteristics of a styrenic polymer having a syndiotactic configuration, while the use of a trivalent titanium compound unfavorably necessitates a further purification step, that is, the removal of a styrenic polymer having an atactic configuration.
As mentioned hereinbefore, the valency of titanium in the titanium compound to be used for the preparation of a catalyst has a pronounced effect on the stereoregularity of the polymer to be produced. It is known that in the production of an isotactic polypropylene, as opposed to the production of a styrenic polymer having a syndiotactic configuration, the use of a tetravalent titanium complex leads to the production of a polymer having a low stereoregularity only and the catalyst system having a high activity and causing a high regularity of the polymer is of a trivalent titanium compound system.
Under such circumstances, intensive research and investigation were continued by the present inventor in order to develop a process capable of efficiently producing a (co)polymer of an aromatic vinyl compound having a high degree of syndiotactic configuration by the use of a catalyst system which is prepared by using a trivalent titanium compound.
As a result, it has been found by the present inventor that a (co)polymer of an aromatic vinyl compound having a high degree of syndiotactic configuration and a low degree of atactic configuration can efficiently be produced in high activity by the use of a catalyst which comprises (1) a catalyst component obtained by contact-mixing, in advance, a trivalent titanium compound and a definite compound, (2) at least one catalyst component selected from the group consisting of an ionic compound comprising a noncoordinate anion and a cation, an aluminoxane and an organoboron compound and optionally (3) a Lewis acid. The present invention has been accomplished by the aforesaid finding and information.